Plant Nutrition- What Are Fertilizers & How to Choose the Right One?

Plant nutrition is one of the most important fields to understand if you are a passionate gardener. What are fertilizers and how does it provide nutrition to plants? We frequently hear the terms fertilizers, manures but often do not understand the differences and applications of each.

There are numerous types and brands of fertilizers available in the market. Do you often get confused about which one should you buy to provide a proper plant nutrition? This article will help clear the confusion and help you make the right choice.

Fertilizers are essential substances that provide nutrition to a plant. Like humans require all the vitamins and minerals for proper growth, in the same way, plants require some nutrients for their optimal growth. Examples of fertilizers are cow dung compost, vermicompost, NPK, etc.

Plant Nutrition

To understand what are fertilizers and which fertilizer is best for your plant or the meaning of fertilizer, you must first understand the composition of a plant.

All organic material on this planet is made up of 4 basic elements namely Hydrogen, Oxygen, Carbon, and Nitrogen. In fact, 90% of a plant’s dry weight consists of these 4 elements.

Our atmosphere and environment have most of the plant nutrients available in abundance. The atmosphere consists of 78% Nitrogen, 21% Oxygen, 2% Carbon and the rest are all other elements. Water consists of 2 parts Hydrogen and 1 part Oxygen.

• Carbon: Constitutes ~50% of the plant’s dry weight. It is found in chlorophyll (green pigment of plants), cell walls of plants, and sugars produced by plants.
• Oxygen: Essential for the formation of cellulose, starch, and sugars. It is required by plants for respiration which provides energy for growth to plants.
• Hydrogen: Required for nutrient exchange. It is available in the form of water and is necessary for plants to maintain turgor pressure (Have you seen how a plant withers and wilts when lacking sufficient water)

A plant must have access to all the required elements/nutrients for it to grow. Lack of any of the plant nutrients will lead to poor growth. Lack of plant nutrition may result in stunted growth, yellowing of leaving, falling of leaves, no fruit formation, falling of new buds, or even death of the plant!

Nutrients required by plants can be classified into 2 types:

• Macro Nutrients
• Micro Nutrients

Plant Nutrition: Part 1

Macro Nutrients For Plants

Macronutrients are substances required/absorbed by plants in large quantities for their survival and growth.

List of macro nutrients for plants

• Nitrogen (N):
  • Required for the creation of chlorophyll, amino acids, and coenzymes.
  • Lack of nitrogen will lead to weak elongated plants (also called spindly plants). The leaves will be small and may turn yellowish. Parts of plants may become purple in color.
  • Excess nitrogen will cause vigorous growth, leaves will be dark green in color and the ripening of fruits may be delayed. The plant becomes more prone to pest attacks.
• Phosphorous (P):
  • Helps in flower and fruit production, root growth, production of sugars, and energy
  • Lack of phosphorous causes stunted growth. The root system becomes weak. The plant becomes dark green in color, the lower side of the leaves turn yellow ( may have purple shade as phosphorus is drawn from the old leaves to enable new growth). The leaves start curling backward and droop. Fruit formation is affected.
  • Zinc and copper absorption will reduce when excess phosphorous is supplied to plants
• Potassium (K):
  • Helps in protein synthesis, sugar, and starch. Required for root growth and hardiness of plants
  • Deficiency of potassium leads to slower growth of plants while old leaves develop spots ( called leaf mottle). Fungus attack becomes prominent.
  • Excess potassium reduces the absorption of magnesium.

Plant Nutrition: Part 2

Micro Nutrients For Plants

Micronutrients are substances required by plants in small quantities for their survival and growth.

List of micro nutrients for plants

• Calcium
  • Required for the formation of cell wall
  • Lack of calcium leads to withering and drooping of young shoots and falling of blooms from the plant. It leads to stunted plant growth and crinkle in leaves.
• Magnesium
  • Helps in the production of chlorophyll and formation of enzymes
  • Lack of magnesium leads to curling of old leaves and yellowing between the veins of the old leaves while the new leaves remain green as they suck magnesium from the old leaves.
• Sulfur
  • Acts as a fungicide in natural form. Helps in seed and fruit formation, protein synthesis, and water uptake.
  • Lack of sulfur leads to young leaves turning yellow/purple.
  • Excess sulfur leads to slower growth and smaller leaves.
• Iron
  • Helps in chlorophyll formation and respiration of plants to create growth energy.
  • Iron deficiency leads to a drop of blooms from the plant, pale new growth, yellowing between veins of the plant, and dying of leaves from the sides.
• Boron
  • Helps in cell wall formation in combination with calcium.
  • Lack of boron leads to the brittleness of stems and slower growth of the plant.
  • Excess of boron leads to tips of leaves becoming yellow and ultimately die.
• Manganese
  • Helps faster growth of plant and oxygen generation during photosynthesis.
  • Lack of manganese leads to yellowing of leaves between veins and the dropping of blooms from the plant.
  • Excess of manganese leads to lesser absorption of iron.
• Zinc
  • Helps in respiration, nitrogen production, and chlorophyll formation in plants.
  • Deficiency of zinc leads to smaller leaf formation and crinkled leaf margins
  • Excess zinc leads to lesser absorption of iron.
• Copper
  • Helps in enzyme activation, photosynthesis, and respiration.
  • Lack of copper leads to pale leaves with yellow spots
  • Excess of copper leads to lesser absorption of iron
• Molybdenum
  • Helps in the processing of nitrogen
  • Lack of molybdenum leads to smaller and yellow leaves
• Cobalt
  • Required in small amounts by bacteria which fix nitrogen in plants.

Note: Classification of plant nutrients into macronutrients and micronutrients does not mean that one nutrient is more important than the other. It just indicated the relative quantities required by plants.

Soil pH

Plant nutrition will fail if you do not maintain the pH of soil as per the plant type.

Soil pH affects the absorption of nutrients. Hence if a plant is not able to absorb the nutrients from the soil, no matter how balanced nutrition you provide to the plant, it will do no good to your plant.

Every plant has a different requirement of soil pH. Hence plan your soil type as per the plant you plan to grow.

A high pH leads to reduced absorption of Iron, Boron, Manganese, Zinc, Phosphorous and Copper.

A low pH leads to reduced absorption of Potassium, Calcium, Sulphur, Magnesium and Phosphorous.

Hence an optimal and balanced soil pH is an important factor in the field of plant nutrition.

Soil Temperature

At high temperatures, the dissolved oxygen in water reduces and hence roots of the plant do not get sufficient oxygen.

A soil temperature of 64-76 F (17-24 degree C) is ideal for plant growth in general.

Notes on Plant Nutrition

A plant goes through various stages of growth. It is important to note that not every stage of plant growth will have same nutrition requirements.

During the vegetative stage i.e. when the plant starts producing foliage, it needs more Nitrogen as Nitrogen helps to produce chlorophyll and helps in leaf formation. Hence Nitrogen fertilizers are best at this stage of growth.

During the reproductive stage i.e. when the plant starts producing flowers, seeds and fruits, it needs more of Phosphorous and Potassium.

What Are Fertilizers?

Fertilizers are substances added to soil/growing media to provide required nutrients to plants. They may be man-made or naturally occurring in environment/nature.

When you grow plants in the growing media/soil, plants take nutrients from the media/soil depleting the media/soil of those nutrients. Fertilizers are added to growing media/soil to replace those nutrients or increase the soil fertility.

Types Of Fertilizers

Based on the origin, fertilizers can be classified mainly into 2 types:

• Organic: Mainly derived from animal or plant matter. Example cow dung cakes, bone meal, human excreta, vermicompost, etc.
• Inorganic / Chemical / Synthetic: Man-made fertilizers like urea, NPK fertilizers, etc.

Nitrogen Fertilizers

By now, you have got an idea of how important Nitrogen is for the plants. Although it occurs abundantly in the atmosphere in the form of gas, plants cannot absorb it in its natural form. There is a class of useful bacteria that convert Nitrogen to a useful form.

Inorganic/Chemical Nitrogen fertilizers are mainly derived from a compound called ammonia.

Difference Between Manures and Fertilizers

Fertilizer is anything that increases soil fertility or provide plant nutrition. By this definition, even manure is a type of fertilizer.

However, in common parlance, manure is an organic material produced when dead animals and plants decompose under the soil whereas fertilizer normally refers to inorganic or synthetic fertilizers produced in factories.

Comparison between fertilizers and manures:

S.No.	Fertilizers	Manures
1	Created in factories	Occur naturally
2	A high concentration of nutrients	A low concentration of nutrients
3	Need to be applied as per prescribed guidelines	Do not need any special instructions to apply
4	Harms soil microbes when applied in large quantities	Does not harm soil microbes
5	Does not add humus	Adds humus

If you would like to share your thoughts or queries, please leave a reply in the comment section below.